1. Field of the Invention
The present invention relates to a control system which is effective in case of failure of fuel injection units for internal combustion engines, particularly Diesel engines.
2. Description of the Prior Art
Fuel injection control systems heretofore known for use in multiple-cylinder internal combustion engines have been so designed that a fuel injector having an electric actuator is provided for each cylinder and the injection of fuel is controlled separately for each of the injectors in accordance with an electric control signal from a control unit. However, if, for example, a fault occurs in the fuel measuring portion of the fuel injector making it impossible to control the quantity of fuel injected or increasing the quantity of fuel injection, the engine is caused to overrun and a very dangerous condition results. However, these control systems have no preventive function to overcome these difficulties. Also, when a fault occurs so that the injection of fuel into any of the cylinders is stopped suddenly, it is no longer possible to maintain the balance of the engine setting it into abnormal vibration and the known control systems cannot prevent it.
In particular, if the above-mentioned fault in the fuel metering portion renders the fuel injection control inoperable with the injection quantity being increased, the engine is caused to overrun and there is possibility of endangering life in some cases. Particularly, even in the case of electronic control systems, their safety functions amount to no more than cutting off the injection of fuel and stopping the engine operation upon occurrence of such fault. However, these safety functions have the following disadvantages and do not meet the needs of the users in recent years. In other words, if such fault occurs during the running on an express-way, winter mountain road or deserted agricultural road or where the engine is used as a driving source for the hydraulic power supply of the hydraulic units in operation, the stopping of the engine gives rise to secondary hazards. As a result, even such a fault occurs, it is important to keep the engine operating by overcoming all difficulties and find one's way to a safe place.